1. Technical Field
The present invention relates to forward error correction (FEC) for high-speed serial optical transport and, in particular, to systems and methods for reduced-complexity FEC decoding with low-density parity check codes.
2. Description of the Related Art
In the recent years, with the rapid growth of data-centric services and the general deployment of broadband access networks, the dense wavelength division multiplexing (DWDM) network has been upgraded from 10 Gb/s per channel to more spectrally-efficient 40 Gb/s or 100 Gb/s per channel systems and beyond. 100 Gb/s Ethernet (100 GbE) has recently been standardized. As the communication rate over a given medium increases, transmission becomes increasingly sensitive to errors due to various linear and nonlinear channel impairments such as chromatic dispersion, polarization mode dispersion, and fiber nonlinearities. The Shannon limit for a noise-influenced channel describes a maximum amount of error-free data that can be transmitted with a specified bandwidth—it is therefore helpful to have robust codes and modulation schemes that closely approach the Shannon limit without imposing high requirements in terms of implementation cost and complexity.
Random low-density parity-check (LDPC) codes are difficult to implement because of the lack of regular structure in their parity check matrices. Indeed, implementing a sum-product algorithm to decode LDPC codes at 40 Gb/s is challenging with state-of-the-art very-large-scale integration (VLSI) technologies.